One feedstock source for making renewable distillate products is to use a feedstock that contains triglycerides. Typical triglycerides include a three carbon glycerol backbone that has ester linkages to three longer side chains. Separating the side chains from the glycerol backbone typically results in formation of a fatty acid corresponding to each of the side chains. After separation from the glycerol backbone, many of the fatty acids present in triglycerides can have a chain length that is suitable for use, possibly after further processing, in diesel products such as diesel fuels or diesel fuel additives.
Lubricant base oils are another potential product that can be made from a biomass source. However, triglycerides with fatty acid chain lengths in the lubricant base oil boiling range are currently less common. One option for making a lubricant base oil product from a feed containing fatty acids is to couple two or more fatty acid chains to create molecules with longer chain lengths.
European Patent Application No. EP 0457665 describes performing a condensation reaction on carboxylic acids or polyfunctional compounds such as triglycerides using a catalyst based on an iron-containing mineral, such as bauxite.
U.S. Pat. No. 8,048,290 describes a process for producing branched hydrocarbons. A feedstock derived from a biological starting material, such as a fatty acid or a fatty acid derivative, is subjected to a condensation step to produce hydrocarbons that also contain one or more heteroatoms, such as oxygen or nitrogen. The condensation product is then subject to a combined hydrodefunctionalization and isomerization step. In this combined step, isomerization and heteroatom removal are performed in the same step. Examples of suitable catalysts for performing the combined hydrodefunctionalization and isomerization step include alumina bound ZSM-23 or SAPO-11 with supported Pt as a hydrogenation metal. ZSM-48 is also mentioned as a suitable zeolite.
U.S. Pat. No. 8,053,614 describes a method for producing a base oil. In various options, triglyceride containing feeds are converted to fatty acids or fatty acid alkyl esters. The fatty acids or fatty acid esters are then used to form ketones via a condensation reaction. The ketones are then deoxygenated in a hydrogenation step to form paraffins, which were then isomerized. One or more distillation or separation steps are included at various points in the process of converting the triglyceride containing feed to the isomerized paraffin.